New enzymes, new pathways and an alternative view on starch biosynthesis in both photosynthetic and heterotrophic tissues of plants

Since the initial discovery showing that ADPglucose (ADPG) serves as the universal glucosyl donor in the reaction catalyzed by starch synthase, the mechanism of starch biosynthesis in both leaves and heterotrophic organs has generally been considered to be an unidirectional process wherein ADPG pyro...

Full description

Saved in:
Bibliographic Details
Published in:Biocatalysis and biotransformation 2006-01, Vol.24 (1-2), p.63-76
Main Authors: José Muñoz, Francisco, Teresa Morán Zorzano, Maria, Alonso-Casajús, Nora, Baroja-Fernández, Edurne, Etxeberria, Ed, Pozueta-Romero, Javier
Format: Article
Language:English
Subjects:
ADPglucose
ADPglucose pyrophosphorylase
Bioconversions. Hemisynthesis
Biological and medical sciences
Biotechnology
Calvin cycle
Fundamental and applied biological sciences. Psychology
Methods. Procedures. Technologies
starch
starch turnover
sucrose
sucrose synthase
Citations: Items that this one cites
Items that cite this one
Online Access:Get full text
Tags: Add Tag
No Tags, Be the first to tag this record!
Description
Summary:Since the initial discovery showing that ADPglucose (ADPG) serves as the universal glucosyl donor in the reaction catalyzed by starch synthase, the mechanism of starch biosynthesis in both leaves and heterotrophic organs has generally been considered to be an unidirectional process wherein ADPG pyrophosphorylase (AGPase) exclusively catalyzes the synthesis of ADPG and acts as the major limiting step of the gluconeogenic process. There is however mounting evidence that ADPG linked to starch biosynthesis is produced de novo in the cytosol by means of sucrose synthase (SuSy). In this review we show and discuss the numerous pitfalls of the 'classic' view of starch biosynthesis. In addition, we describe many overlooked aspects of both ADPG and starch metabolism. With the overall data we propose an 'alternative' model of starch biosynthesis, applicable to both photosynthetic and heterotrophic tissues, according to which both sucrose and starch biosynthetic processes are tightly interconnected by means of an ADPG synthesizing SuSy activity. According to this new view, starch metabolism embodies catabolic and anabolic reactions taking place simultaneously in which AGPase plays a vital role in the scavenging of starch breakdown products.
ISSN:1024-2422
1029-2446
DOI:10.1080/10242420500518839